TPS62130A-Q1: NO OUTPUT

Sherry,

Is there no SS cap on this design? C307 says "Do not stuff". You need to install a CSS cap - I recommend 3300pF as a start. 

What part numbers are you using for L300, C304, C306, C308 and C309? 

Does the design work with no USB plugged at the load?

Thanks,

Amod

Hi Amod,

The load is as below. They tried to add a 4.7nF CSS cap, but no use. There is a phenomenon, when the customer plug in USB firstly and then power on our device, our device can work normally. When the customer power on our device firstly and then plug in USB, our device will be broken.

Thanks & Best Regards,

Sherry

Hi Sherry,

If the order in which device is powered vs USB is plugged in, it would be good to see some waveforms to understand the situation. The schematic and components look fine.

1. When you say device is broken, what does it exactly mean? Is the device damaged or can the same device power up if USB is plugged in first and device is powered? 

2. We might get some insight if you can share VIN, VOUT, SW, IL (inductor current) waveform during both cases

• USB is already plugged in and then device is powered - share the startup waveforms 
• device is powered first and then USB is plugged. - share the waveforms when USB is plugged

Thanks,

Amod

Hi Amod,

We think the device is broken because we can't restart the device. The device's output is always 0.

In addition, we tried to test one new 62130 today, and this device still works normally even though hot plug the USB load several times. But last week 10pcs device have been broken with the same operation. We test power up waveform on this good device as below the first picture. The waveform is same at below two phenomenon,

• USB is already plugged in and then device is powered - share the startup waveforms 
• device is powered first and then USB is plugged. - share the waveforms when USB is plugged

Firstly, power on 62130, and then plug in the USB load, the waveform is as below,

Thanks & Best Regards,

Sherry

Hi Sherry,

Thank you for sharing the additional information. The waveforms look fine to me except a couple things.

Is the CSS installed while doing this test? The startup seems rather quick with inductor current hitting both the reduced current limit (~1.6A) initially when VOUT < 0.5V and then 3.6A later. Also, the VOUT seems to overshoot to high values (>6V) due to this. So, it will be good to reduce stress by having a CSS cap which will give you a smoother startup.

Also, since the design is for 5V, I would double check why the VOUT values look higher than that ( 5.68V and 6.08V as per scope measurements below). It could be related to measurement but can you confirm the DC value using a multimeter is close to 5V when the IC is regulating?

For the damaged units, you can send them for FA to find more about the damage. 

Thanks,

Amod